The granules that are so frequently found in leucocytes generally seem to lie scattered quite irregularly in the cytoplasm of the cell in which they occur. It is possible, in the case of the leucocytes found int he spleen, lymphatic glands, and the blood of mammalia, that there never is any ordered arrangement of the granules. In the bone-marrow, however, where leucocytes containing granules are often extremely numerous, a section of properly preserved material will show that the granules in a large proportion of these cells are arranged in a more or less definite manner. The granules in these are, as a rule, oval in shape, and are seen to lie in sequence close to each other, so that a line drawn through their long axes would appear as a thread or wire coiled up irregularly in the cytoplasm of the cell (fig . 1.). Given this line connecting them, the granules would exactly simulate beads threaded on a wire bent into irregular curves, and put into a small spheroidal space. There are many gradations in the regularity of this arrangement of the granules. It varies from the mere suggestion of some of them having been strung together to very definite order, and the joining of several end to end (fig. 2). There are, again, other cells in which a large number of the granules are joined together, forming in places a thick, deeply-staining thread, the axis of which is continuous with the axis of the strings of separate granules (fig. 3). In some such cells the separate granules and the thick thread appear to be about equal in amount and continuous with each other fig. 4), while in others there are but very few granules, and the thread preponderates. From these it is possible to pass, by almost insensible gradations, to cells where there are no granules, but only a thick thread coiled up around the nucleus (fig. 6). In some of these cells it is practically impossible to distinguish the nucleus, so dense and darkly-staining is the coiled thread (fig. 5). So misleading are these figures that for several months I took them for, and drew them as, the spireme stages in the prophase of division in which the nuclear membrane had disappeared. It was only when I found nuclei in a resting condition existing int he cells which also contained this thread, that the present interpretation was arrived at. A careful examination of the cells in this stage, however, will frequently, though not always, demonstrate the presence of a resting nucleus. Where the nucleus cannot be seen, the reason is generally very obvious: the thread is so deeply stained with the basic stain, and is so closely coiled, that it entirely obscures the similarly stained nucleus. Moreover, while the thread stains very deeply, the nucleus, apparently, stains less readily than usual, thus adding to the probability of its being overlooked.